Chelsea are not giving up on their pursuit of midfielder Luka Modric and are expected to lift their offer to £30m in the next few days, despite Tottenham's repeated insistence that the Croatian is not for sale.

In what is becoming a bitter struggle, Modric upped the stakes by handing in a transfer request earlier this week, on the day he joined the Spurs squad to fly out on a pre-season tour to South Africa. It was refused.

Spurs are becoming increasingly angry at Chelsea's persistence, having rejected their bids of £22m and £27m, and insisted they will not listen to offers for a player who 12 months ago put pen to paper on a six-year deal.

Manager Harry Redknapp said: "We know he wants to leave and whether he writes it down on a piece of paper doesn't really make any difference to our stance." Captain Michael Dawson claims the atmosphere in the squad remains healthy, despite Modric's desire to leave.